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J Occup Health year 2003 volume 45 number 4 page 209 - 214
Classification Original
Title Critical Dose of Lead Affecting delta-Aminolevulinic Acid Levels
Author Katsuyuki MURATA1, Tadashi SAKAI2, Yoko MORITA2, Toyoto IWATA1 and Miwako DAKEISHI1
Organization 1Environmental Health Sciences, Department of Social Medicine, Akita University School of Medicine and
2Occupational Poisoning Center, Tokyo Labor Accident Hospital, Japan
Keywords Lead, Critical dose, Adverse effect, delta-Aminolevulinic acid, Occupational exposure, delta-Aminolevulinic acid dehydratase
Correspondence K. Murata, Environmental Health Sciences, Department of Social Medicine, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan
Abstract Critical Dose of Lead Affecting delta-Aminolevulinic Acid Levels: Katsuyuki MURATA, et al. Akita University School of Medicine-To estimate the critical dose of the association between the blood lead concentration (BPb) and delta-aminolevulinic acid (ALA) levels, ALA levels in plasma (ALA-P), blood (ALA-B), and urine (ALA-U), and the activity of delta-aminolevulinic acid dehydratase (ALAD) were determined in 186 Japanese lead workers, aged 18-62 yr, with BPb levels of 2.1-62.9 microg/dl. For this purpose, the benchmark dose (BMD) method, recently used in the environmental health field in place of the no-observed-adverse-effect level, was introduced into this study. The BMD was defined as the BPb level that resulted in an increased probability of abnormal change in ALA-related parameters by an excess risk (BMR) of 5% in exposed workers i.e., from P0 (abnormal probability of 5% in unexposed workers) to P0+BMR for exposed workers at the BMD. ALA-related parameters were significantly correlated with BPb. The BMDs computed from the 186 workers, after controlling for age, were 15.3-20.9 microg/dl for ALA levels, and 2.9 microg/dl for ALAD; likewise, the BMDs from the 154 workers with BPb levels of less than 40 microg/dl were 3.3-8.8 microg/dl for ALA levels, and 2.7 microg/dl for ALAD. Since the cutoff value of ALA-P, computed from the latter workers, seems to be closer to the upper normal limit in unexposed adults than does that from the former workers, it is suggested that the critical dose of BPb causing the increased levels of ALA is below 10 microg/dl. Such critical doses are necessary to promote preventive activities of adverse effects of lead.